I've made them, love them, and will continue to do so. They are some of my best performing and aesthetically pleasing bows and outperform even glass bows of identical design and weight.
After using lams of various woods, it seems that what the core and belly lams do isn't as cut and dry as 'filler' and 'compression resistance', IMO. A flexing piece of wood is a very dynamic thing, with tension, neutral, and compression relationships changing throughout the draw and shot. I have made them with the core and belly lams with the same type of wood, and I have made them by mixing them up. I prefer them with bamboo backs and osage core and belly... although bamboo/yew/osage is quite nice too. My bow with the best shooting characteristics is such a bow.
Tri-lams allow us to make exceptional bows with wood that alone, would make something less. That said, nowadays I try to use the very best wood in them I can obtain. They can be bent and glued into shapes that backed bows cannot. Perhaps it's my imagination since I haven't done any formal testing, but they seem to require less wood and mass to make weight and/or reach or surpass the same levels of performance as many others. It's like Perry Reflex squared :^)